A conventional combustible gas turbine engine includes a compressor, a combustor, and a gas turbine. The engine further comprises an outer casing which defines an outer section for each of the compressor, combustor and gas turbine. A rotor extends through the engine. The rotor portion extending through the compressor is defined by a plurality of discs. Each disc can host a row of rotating airfoils, commonly referred to as blades. The rows of blades alternate with rows of stationary airfoils or vanes. The vanes can be mounted to the casing via one or more vane carrier assemblies. A clearance is defined between tips of the blades and an inner surface of vane carrier support panels. During operation of the gas turbine engine, fluid leakage through this clearance contributes to system losses, decreasing the operational efficiency of the engine. It is desirable to keep the clearance as small as possible to increase engine performance. However, it is necessary to maintain a clearance between the rotating and stationary components to prevent rubbing between the rotating and stationary components, which can lead to component or engine damage.
The size of the clearance can change during engine operation due to differences in the thermal growth response times of the compressor moving parts and that of the stationary structure. For example, the thermal growth response time of the stationary structure (e.g., the vane carrier assembly to which the vanes are connected) is significantly quicker than that of the rotating structure (rotor). Thus, the stationary structure has a faster thermal response time and responds (through expansion or contraction) more quickly to a change in temperature than the rotating structure.